The Type 123 has a horizontal filter chamber with similary positioned filter tubes. Influent enters the cover area and is distributed downward through the tubes, where it passes through the tubes from the inside to the outside, depsoitiing solids in the inner tube surfaces. The filter is cleaned manually, by removal and replacement of inexpensive liners within each tube. Chambers are available in a varety of materials including, rubber-lined steel, stainless steel, or exotic alloys. Filter tubes are availabe in stainless steel and other corrostion resistant materials using cloth and paper tube ilners. resistant materials, using cloth and paper tube liners.

Advantages of the Type 123:
- Inexpensive design
- Conveneitent disposable media
- ideal for polish and trap filtration